This is relatively **brutal**. You run all stuff within ```spec/{controller,model}/*_spec.rb``` to kill **each** mutation. Isn't there a possibility to somehow at least select a specific spec file per mutation? You can access the ```mutation.subject``` and descending properties to identify the class being mutated. The class needs to be identified as controller or model, than you can expand this onto ```spec/models/foo_spec.rb``` for ```Foo``` model or ```spec/controllers/bar_spec.rb```.for ```Bar``` controller.